Stored Product Insect in Jar

Insect pests for stored product


I’m sharing with you all an article written by my talented and knowledgeable colleague, Andy Hamilton-Smith. This is part 1 of a series he is writing for Professional Pest Manager magazine on getting to know your pests, with this month’s focus being on stored product insects. 

Next in the series is due in September, so make sure you check back then!


Andy Hamilton-Smith
Senior Field Biologist Rentokil Pest Control

Stored Product Insect in Jar
Pantry moth larvae in sesame seeds

Ever since Man added to his skills as a hunter, and became proficient as a gatherer and cultivator, he has been faced with the problem of sharing the fruits of his labour with unwanted guests such as rats, mice and cockroaches. As pest managers, we are all familiar with the identification and control methods used to rid ourselves of these pests, and have become experts in the inspection techniques required to find them in the first place. I wonder though, how many of us are missing out on another source of income, by overlooking the potential that is locked up in the mostly ignored market of Stored Product Insect (SPI) pest management in Australia? Too small to see, too difficult to find, too many species to get to know and identify, and so what if you have found some “weevils” in the pantry? Just throw the infested material away, clean out the cupboard and I can move on and earn some decent money inspecting and treating termites!

In the following article I will give you an introduction to the biology and identification of the common pest species, inspection and monitoring techniques and control, plus the role that good hygiene practice plays in the success of the overall program.

Firstly, what are ‘stored products’?

Stored products are foodstuffs that man has made or harvested and intends to use in the future. Examples would include grains, cereals, pasta, flour, dried fruit and nuts, processed meats, coffee and tobacco (though tobacco production in Australia is now a dying industry… pun intended!).

Where are stored product insects (SPI) found?

Indian Meal Moth
Indian Meal Moth

They are found in many different situations, including domestic residences, commercial and catering establishments, manufacturing, hospitality, industrial sites, agriculture, and in modern transport such as ships, planes and trains. The difficulty in finding them though is always a problem, not only because of their small size, but also because SPI tend to live in the product itself, as well as in the product storage and food processing equipment. They also prefer to hide away from light, particularly in those areas that we now collectively refer to as “Confined Spaces”, but more on that later.

SPI commonly belong to the insect orders Coleoptera (beetles and weevils), Lepidoptera (moths), Psocoptera (booklice) and the Arachnida order, Acarina (mites). We also classify them as primary or secondary pests. Primary pests are those insects that attack whole grain and complete their life cycle within the grain such as rice weevil, grain weevil and lesser grain borer. Secondary pests complete their life cycle in milled, broken or processed products, with examples being confused flour beetle, sawtooth grain beetle and drugstore beetle. Their speed of development is dependent on environmental factors including temperature, humidity and quality of their food source, and varies from species to species. During the warmer months, development from egg to adult for most species can take as little as six weeks.

As with any pest management program, the first step is to complete a thorough inspection. To assist us with this I recommend using the following equipment that will easily fit into a small backpack or waist bag.

  • Torch and Headlamp (headlamp is useful when having to climb access ladders).
  • X10 Hand Lens (SPI are small insects and a lens is essential).
  • Small craft type paintbrush and tweezers (for picking up small delicate insects).
  • Specimen tubes (SPI easily get crushed when plastered between two pieces of sticky tape or placed in a pocket for later identification).
  • Chemist Spatula or flat blade (for lifting and removing compacted residues that may hold live insects).

It is useful to have access to a microscope; modern units can now connect to your laptop, where you can view your specimens up to a 120X magnification and record images and save directly into your files. I picked mine up at a hobby shop for around $160, not a bad investment for any pest manager.

As well as the above, in most facilities you will probably be issued with a dustcoat or overalls, head covering and hearing and eye protection before you will be allowed into production and storage areas. Please also remember, that in many commercial food-manufacturing facilities they will not allow loose items to be carried in pockets that may fall out and contaminate their product. As a young field biologist in the UK I somehow managed to lose a valuable fountain pen (that’s giving away my vintage) that escaped my top pocket and fell through the hatch of a flour silo during an inspection in a flourmill in Kent. Imagine some lucky customer’s glee when on opening a kilo bag of plain flour they realised they had won a Mont Blanc pen worth a hundred quid!

Drugstore-Beetle-DamageWhere to look during the inspection?

Everywhere access is available! In the good old days a cellar was a cellar, a lift well was a lift well and a bakery cooler was just a big old cooling cabinet full of breadcrumb and old loaves that played home to hundreds of individual SPI. Nowadays, all are classified as a ‘Confined Space’, and we must have various permits and safety training before access is allowed, otherwise we are left to stand outside the equipment and guess what might be hiding within.

The main thing during the inspection is to think small, examine those small cracks and crevices in which product debris can collect and attract SPI and be prepared to ‘think outside the square’. I know a technician, who after several visits to the same residential property where they were experiencing a problem with drugstore beetle, having been through the usual routine of checking the kitchen cupboards and elsewhere through the house, eventually found the beetles living and multiplying quite happily in the door draft excluders that had been filled with wheat!

Also remember during your inspection that most production equipment will be fitted with trip switches so that for safety reasons, when doors or panels are opened, the production process comes to a grinding halt. Just after losing my fountain pen, I learnt this lesson the hard way by opening the safety gate on a production line during a night inspection at a biscuit manufacturer in London. By the time the maintenance crew had resolved the ‘problem’ and had got production moving again, several thousand biscuits had burnt to a cinder whilst left on the stationary conveyor belt in the oven. Thank goodness the Emergency Exit door through which I made my escape into the night wasn’t alarmed!

We’ll leave things there as I disappeared into the night, and in the next segment we’ll take a look at the common pest species, and how we go about controlling the ‘Evil Weevil’.


1 Comment

  1. Great artical Andy, Just searching for your email and come across your great artical. Anyway I will send you the termite pictures I was talking to you about, shortly, Cheers Aaron.

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